176 PREDACIOUS AND PARASITIC ' 



doubtless, to assist in securing the organ in position in the body 

 of the victims of attack. 



The insertion of the setge in the skin of the aphis or other 

 insect being accompHshed, these serrations give a secure hold, and 

 enable the channelled lancets within, sliding one upon the other 

 by the action of the spiral muscles at the base of the rostrum, to 

 extract at leisure the juices of the body without disturbance or the 

 possibility of escape for the victim. It is generally considered 

 that these four setae should be taken to represent the mandibles 

 and maxillae of the Diptera and Hymenoptera ; but this view does 

 not seem to take cognisance of the resemblance in structure 

 between the grooved lancets and the narrow grooved, horny ligula 

 of the Diptera. It seems to me that the upper of the two lancets 

 may represent the united and elongated mandibles, whilst the 

 lower is most probably the representative of the ligula. All four 

 setae take their rise from among powerful groups of muscles, 

 situated in either side of the head, and as shown in Fig. lo are so 

 divergent as to give each one an entirely independent point of 

 support, while, centrally placed among them, the tube of the 

 lancets is continued as a pharynx surrounded by spiral muscles, 

 which, by their contraction or elongation, would be capable of 

 producing a powerful pumping action exactly suitable to the 

 action of the lancets. 



The coxae, and especially the anterior pair, are very largely 

 developed in the Capsidct, and as this feature is generally evident 

 in the earlier stages of the insect's existence, it may often assist in 

 determining the position of an unknown larva or nymph. The 

 tibiae, alike in the nymph and imago, are slender, and usually, 

 though not always, possess a fringe of five spines, and the tarsus 

 is in all genera three-jointed. The posterior protuberance is less 

 prominent in the nymph than in the larva, but presents much the 

 same features ; but the ventral surface of the abdomen, in all 

 those Capsida which I have examined at this later stage, shows in 

 the female an axial ridge sufficiently indicative of the future ovi- 

 positor. The tufted prominences on the upper surface of the 

 abdomen are, in the species illustrated, marked by dark spots of 

 irregular size, and to get a proper observation of these a specimen 

 should be treated with potash and mounted in Canada balsam, 



